Refractory casting tube for casting hot liquid metals

ABSTRACT

The invention relates to a casting tube for casting hot liquid metals and to a process for producing such casting tube. The casting tube comprises a casting tube head to be immersed below the casting level in the mould and having a closed bottom and at least one canal extending in lateral direction from the inner bore of the casting tube to which a vertically upwardly extending canal is joined whose length amounts to at least 4 cm. Such casting tube guarantees an excellent exclusion of non-metallic particles contained in the metal.

United States Patent Hoyer et al.

REFRACTORY CASTING TUBE FOR CASTING I-IOT LIQUID METALS Inventors: Otto Hoyer; Erwin Kuebel, both of Linz, Austria [73] Assignee: Vereinigte Osterreichische Eisenund Stahlwerke Alpine Montan Aktiengesellschaft, Austria Filed: Feb. 1, 1973 Appl. No.: 328,504

[30] Foreign Application Priority Data Feb 3, 1972 Austria 857/72 U.S. Cl 222/566; 164/281 Int. Cl B22d 11/10 Field of Search 222/566, 567; 164/133,

[56] References Cited UNITED STATES PATENTS 12/1934 Nock, Jr. 164/337 5/1971 Mills et al. 164/281 51 May 13, 1975 3,587,719 6/1971 Schrewe et al. 164/337 X 3,703,924 1 1/1972 Whisler et a1 164/337 FOREIGN PATENTS OR APPLICATIONS 638,931 6/1932 Germany 164/133 741,740 11/1943 Germany .1 164/135 Primary Examiner-Robert B. Reeves Assistant E.\'aminerDavid A. Scherbel Attorney, Agent, or Firm-Brumbaugh, Graves, Donohue & Raymond [57] ABSTRACT 2 Claims, 6 Drawing Figures PATENTED HAY I 3 i975 SHEET 3 0? 3 REFRACTORY CASTING TUBE FOR CASTING HOT LIQUID METALS The invention relates to a refractory casting tube for casting hot liquid metals. in particular for continuously casting bars from steels destined for the production of cold rolled sheets, comprising a casting tube head to be immersed below the casting level in the casting form. said casting tube head having a closed bottom and at least one canal extending in lateral direction from the inner bore of the casting tube for deflecting the metal. and to a process for producing such casting tube.

Casting tubes of this kind are used particularly in continuous casting of steel slabs. They serve for creating below the casting level in the mould a directed current so that nonmetallic inclusions and desoxidation products are flushed to the surface of the steel where they get in contact with a casting powder or slag layer floating on the steel surface and are absorbed by it. According to the inclination of the axes of the outflow canals various current directions may be obtained as this is described e.g. in Concast-News," Vol. 7. 2/l968, p. and 6, or in STA|" (German edition) I967, issue 2. pages I39-l4l, and in the U.S. Pat. Nos. 3.517.726 and 3,37 l .704. Such casting tubes may also be used for a primary separation of non-metallic particles in a tundish arranged before the mould.

The known casting tubes have the disadvantage that the metal current in the mould cannot be satisfactorily directed and cannot or only with greater difficulties be adapted to varying bar dimensions. When slabs are cast, often the liquid metal does not get to the side walls of the mould or to the surface of the casting level so that the separation of non-metallic inclusions from the metal is not guaranteed. Owing to the erosion caused by the liquid metal also the contours of the outflow openings are greatly changed in the course of casting so that the conditions for the formation of the desired directed current are impaired.

The invention is aimed at avoiding the described disadvantages and difficulties and in a refractory casting tube of the kind defined in the introduction resides in that to the laterally extending canal or to the laterally extending canals a refractory canal extending vertically upwardly is joined whose length amounts to at least 4 The casting tube according to the invention is particularly sutiable for continuously casting steels destined for the production of cold rolled sheets with highest surface quality, in particular of sheets which are subjected to cold shaping. Their composition may be e.g. the following: up to 0.20 C, 0.25 to l.(i0 Mn. 0.02 to 0.1 "/0 Al and if desired up to 0.30 Si. balance iron and customary impurities.

According to a preferred embodiment. in the casting tube head two vertically upwardly extending canals are provided arranged diametrically opposed to each other relative to the central inner bore of the casting tube. When slabs are cast having a width of more than l.5 m, such casting tubes may be arranged side by side. the axes of the vertically upwardly extending canals lying in a vertical plane laid through the horizontal longitudinal axis of the continuous casting mould.

The invention further relates to a process for producing such casting tubes. which provides for essential advantages. The process according to the invention starts from the known method, according to which the casting tube is produced by pressing refractory material in a die by employing a mandrel corresponding to the bore of the casting tube or by casting refractory material into a casting form by employing a core corresponding to the bore of the casting tube. whereupon the blank or cast product is burnt. and is characterized in that together with the inner bore of the casting tube also the vertically upwardly extending canal or the vertically upwardly extending canals are produced by employing mandrels or cores corresponding to these canal bores by pressing or casting.

Preferably the casting tube head is bored through and the bore opening is closed in the outer wall of the casting tube head after burning the blank or cast product.

Preferably the bore. provided in the casting tube head is directed in a manner that its axis intersects the casting tube axis and the axis of at least one canal extending vertically upwardly.

In order that the invention may be more fully understood several embodiments shall now be deseribed with reference to the accompanying drawings.

FIG. I is a vertical sectional view of a casting tube blank, by means of which the casting tube with a casting tube head comprising two vertically upwardly extending canals is produced.

FIG. 2 is a horizontal sectional view along the line llll of FIG. I.

FIG. 3 shows in enlarged scale the finished casting tube head according to FIG. I in which the vertically upwardly extending canals are connected by a horizontal bore.

FIG. 4 is a horizontal sectional view of a casting tube head with four vertically upwardly extending canals.

FIG. 5 shows a vertical sectional view of a casting tube in casting position with a single vertically upwardly extending canal for deflecting the hot liquid metal.

FIG. 6 shows an advantageous arrangement of two such casting tubes in a continuous casting mould.

The casting tube blank 1 according to FIG. 1 comprises at its upper end an annular shoulder 2, serving for connecting the finished casting tube with the bottom 3 of a ladle or tundish indicated in a broken line. The lower end of the blank 1 has a greater cross section and is denoted with numeral 4; from this broadened end the so-called casting tube head is formed which in continuous casting of steel is inserted at a particular distance below the metal level in a water-cooled continuous casting mould or in a tundish.

This blank I is produced in a first step by pressing plastic refractory material in a die by using three mandrels. whereby the middle mandrel corresponds to the longitudinal extension and the cross section of the casting tube inner bore 7, whereas the other mandrels arranged diametrically opposed to each other relative to said inner bore serve for the formation of the vertical canals 8.9. As may be derived from the drawing. all three canals 7.8.9 end at the same distance from the bottom of the casting tube head 4. In a second step, a horizontal bore I0 is produced which is made to penetrate the casting tube head 4 close to the bottom until a connection between the central inner bore 7 and the vertical canals 8.9 is produced. Then, in a third step, the opening of the bore I0 in the outer wall of the casting tube head is sealingly closed by a stopper 13 of refractory material. Suitably the casting tube head 4 is bored through after the blank I has been burnt. A thread Il may be cut into the opening of the bore [0 to be closed, which thread 11 corresponds to a thread 12 on the stopper 13 so that the stopper may be screwed into the casting tube head e.g. by means of a square pin 14. However, it is also possible to provide the unburnt blank with a bore and to fill out the opening to be closed by a ramming mass which sinters during the subsequent burning of the blank and affords a tight closure.

The casting tube blank may also be produced by casting a pasty refractory mass into a casting form made of e.g. plaster, the greatest part of the humidity of the refractory mass being withdrawn through the porous casting form. Prior to casting, cores are inserted into the casting form which correspond to the inner bore 7 and to the canals 8,9, respectively. The blank or cast product 1 produced by casting is dried then and further processed as described above, i.e. the casting tube head is provided with a horizontal bore to establish a connection between the vertical canals, whereupon the hole in the outer wall of the casting tube head is closed.

The finished casting tube head, represented in FIG. 3 affords a deflection of a metal stream by 180 in upward direction so that during casting two metal streams are obtained which are directed in upward direction and leave the canals below the casting level at a predetermined distance a (FIGS. 5,6). In order to guarantee a sufficiently forced current in vertical direction, the length b of the canals 8, 9 is to amount to at least 4 cm; thus, a is the free" path length, and b the guided path length of the upwardly directed metal streams.

In FIG. 4 a casting tube head 4 is illustrated having four upwardly directed vertical canals l6,17,l8,19 which are connected with the casting tube inner bore 15 by means of laterally extending canals 20,2l,22,23. For producing the connecting canals 20,22 and 21,23 horizontal bores are provided in the casting tube head 4, whose axes intersect the vertical axes of the canals 16,15,18 and 19,15,17, respectively. Numerals 24 denotes the horizontal longitudinal axis of a rectangular mould for casting slabs, whose inner contour 25 is drawn in a broken line. The embodiment according to FIG. 4 represents an advantageous arrangement of the casting tube head 4 for a continuous casting plant for casting slabs.

In FIG. a casting tube 26 is shown from whose inner bore 27 a lateral canal 28 extends providing the connection to a single vertically upwardly extending canal 29. The longitudinal axis 30 of the canal 29 is to coincide with the longutidinal mean axis of the continuous casting mould (not shown) so that a wave or vault 34 is created in about the middle of the casting level 35 by the metal stream 31 directed in upward direction. The distance a between the level 36 defined by the mouth of the canal 29 and the casting level 35, i.e. the free path length of the metal stream 31 flowing out of the canal and its speed v are adjusted in a manner that this wave or vault 34 on the hot liquid metal 32 does not rupture the layer of casting powder or slag covering the metal 32. Thus it is possible to separate satisfactorily non-metallic particles, in particular Al O and SiO from hot liquid metal and to flush them into the layer of casting powder or slag 33. b, the guided path length of the metal stream or the length of the canal 29 amounts to at least 4 cm, as mentioned above.

For continuously casting steel slabs from soft, Alkilled deep drawing steels, it is advantageous to employ two casting tubes 26,26, as illustrated in FIG. 6. The casting tubes are arranged to lie diametrically opposed to each other relative to the bar axis or vertical mould axis 30, so that on the casting level 35 in the watercooled mould 37 two waves or vaults 34,34 are formed. Numeral 38 denotes the solidifying margin of the cast bar which forms in the continuous casting mould 37, which bar is drawn out in downward direction and further cooled until it is completely solidified. When the vertical canals are worn owing to erosion, a change of their cross sections or of the speed v, respectively, may be compensated without difficulties by changing a, i.e. by lifting the casting tube or the tundish, respectively, whereby any change in the effectiveness with which the non-metallic particles are separated is prevented. Since a and v are changeable in relatively wide limits, the casting tubes according to the invention may easily be adapted to various metal throughput amounts/time unit (casting outputs); the ratio between width and thickness of the slab (mould) need not be taken into consideration.

What we claim is: l. A refractory casting tube for the continuous casting of liquid steel in apparatus that includes a continuous casting mould and a tundish located above the mould, said casting tube comprising:

a tube made of refractory material and having an inner bore, 7

the tube being adapted to be secured at one end to the bottom of the tundish so that the inner bore of the tube communicates with the interior of the tundish,

the tube having at its other end a casting tube head that has a closed bottom and at least one canal extending vertically upwardly to define a vertically upwardly directed outlet for the casting tube head, the vertically extending canal being substantially parallel to the inner bore of the tube and having a length of at least four centimeters,

the casting tube head also having at least one laterally extending canal connecting the inner bore of the tube to the vertically extending canal, and

the casting tube being adapted for insertion into liquid steel in the mould during casting and being dimensioned so that the casting tube head and an adjacent lower portion of the tube can be disposed within the mould and spaced from all sides of the mould.

2. The casting tube set forth in claim 1, wherein the casting tube head is provided with two vertically upwardly extending canals arranged diametrically opposed to each other relative to the inner bore of the casting tube. 

1. A refractory casting tube for the continuous casting of liquid steel in apparatus that includes a continuous casting mould and a tundish located above the mould, said casting tube comprising: a tube made of refractory material and having an inner bore, the tube being adapted to be secured at one end to the bottom of the tundish so that the inner bore of the tube communicates with the interior of the tundish, the tube having at its other end a casting tube head that has a closed bottom and at least one canal extending vertically upwardly to define a vertically upwardly directed outlet for the casting tube head, the vertically extending canal being substantially parallel to the inner bore of the tube and having a length of at least four centimeters, the casting tube head also having at least one laterally extending canal connecting the inner bore of the tube to the vertically extending canal, and the casting tube being adapted for insertion into liquid steel in the mould during casting and being dimensioned so that the casting tube head and an adjacent lower portion of the tube can be disposed within the mould and spaced from all sides of the mould.
 2. The casting tube set forth in claim 1, wherein the casting tube head is provided with two vertically upwardly extending canals arranged diametrically opposed to each other relative to the inner bore of the casting tube. 